Two-speed driving mechanism for centrifugal compressors



March49, 1943. H. c. A. Po-rEz TWO-SP'EED DRIVING MECHANISM FOR CENTRIFUGAL COMPRESSORS Filed Mayll, 1939 2 Sheets-Sheet l Illlllll yMillIUNIMHNUIIIUI March 9, 1943. H. Q `A P01-gz 2,313,205 Two-SPEED DRIVING MECHANISM FOR CENTRIFUGAL CoMPREssoRs Filed May ll, 1959 2 Sheets-Shee 2 p yI Znye/Q br Patented Mar. 9, 14943 TWO-SPEED DRIVING M'ECHANISM FOR QENTRIFUGAL COMPRESSORS Henry Charles Alexandre Potez, Meaulte, Somme, France; vested in the Alien Property Custodian Application May 11, 1939, Serial No. 273,151

. `In France June 10, 1938 a claims.V A(c1. 23o-114) In an internal combustion engine for aircraft, which is provided with a mechanically-operated compressor adapted for the restoration of the power atY a certain altitude, the higheris this altitude, the less power will ,be given by the engine on the ground for the same pressure of admission. This difference of power may be as great as for an altitude of restoration of 4000 metres. In these conditions, the take oi power may not be sufficient and this reduction of power must therefore be limited as'far as possible.` One method employed for this purpose consists in providing for an eective over-feeding when on the ground by increasing the admission pressure,.but this greatly increases the strain upon the engine.

Another method, which appears to he the best,

vconsists in varying the speed of the compressor relatively to the engine speed, in order to reduce the loss of power on the ground or at intermediate altitudes.

For example there may be provided a mechan-A ical connecting device having two speeds. The rst speed of the compressor is determined in order to provide for the best conditions of oper- -ation on the ground, and the second speed serves to restore the power at a stated pressure of admission and altitude.

Hitherto, the. two-speed devices have been mounted in the interior of the engine between the rotor of the compressor and the crank-shaft, but this greatly reduced the accessibility required for thesom'ewhat complicated parts, the friction-clutches which these devices usually comprise were in bad condition for the evacuation of the heat generated. Moreover, the two-speed drive was often made with parts having a relatively slow rate of rotation which transmitted heavy torques, thus resulting in a great size and weight. I

The present invention has for its object to provide an improved mechanism for two-speed drive of centrifugal compressors which obviates the aforesaid drawbacks. According .to the invention, the said mechanism is so designed that the speed-changing device can. be located beyond the compressor with reference to the main driving shaft` by which this latter is actuated.

VOwing to this arrangement, the speed-changing mechanism may be mounted ina separatelysecured casing, which is readily removable and accessible, and provides for an effective cooling.

Fig. 1 is a longitudinal section of the aggregate l comprising a compressor and its driving mecha-A nism, improved according to the invention.

Fig. 2 shows the same compressor, in which the driving gear is replaced by a shaft adapted for direct drive. r

In the embodiment shown in Fig. 1, the main driving shaft I (the crankfshaft of the engine or a lay shaft) is connected by a suitable gear set 2, 3, 4, and a driving member or pinion 5 adapted vto increase or reduce the speed, to an auxiliary shaft 6. The pinion 5 engages the shaft 6 by 'bmeans of internal flutes or a splined connection l, and shaft 6 is rotatable in a bearing 8 of the crank-case 9 and in aring ID mounted in the end of a tubular shaft II through which extends axially, from one endl to the other, the shaft 6. It should be noted that a device for limiting the torque is preferably incorporated .into the gear set. 2, 3, 4, 5.

The shaft. llj'through which extends freely and axially the shaft 6, is secured to the rotor I2 and is journalled in bearings I3and I4, which may be ball-bearings. As to the said shaft 6 which is centered in the hollow shaft II by a ring I5, it is journalled at its other end in a bearing I6 of a removable casing I'I which is secured to the suction casing I8 of the compressor. The shaft 6 is slidable longitudinally in the pinion or driving member 5 and the bearing I6.

In the interior of the casing I'I is mounted the mechanism for direct drive and for speedchanging which is adapted to connect in rota.-

In one embodiment, the driving torque is.

transmitted to the speed-changing device by an auxiliary shaft extending axially through the tion the shaft 6 with -the tubular shaft'l I. 'The said mechanism may be controlled by any device of the engine; vat the other end, orices V25 and 21 connectthe said ducts respectively with cham- `43, '45, 46 ata speed which is greater member 30 and the members 3| and 32.

The member 30 is secured to the shaft 6, or is preferably in one piece with` the same, and participates in its longitudinal movements. Two members 33v and 34, which have a tapered form in the interior, are mounted axially on shaft" 6 on either side of the member 30, and can be coupled to the complementary parts 3I and 32a of the members ,3I and 32. Friction facings 33a and 348L may be fitted into the tapered parts the members 33 and 34.

The member 32, 32a is secured, for instance by a tapered t, to a member 35 which is rotatable on the shaft 6 by means of a ring 3S. The member 35 is connected in rotation to the shaft II driving the rotor I2 of the compressor by a uted sleeve or splined connection 31 which extends the member 35 and engages the member 39 secured to the shaft II.

The member (3|, Bla) is secured to a member 40 which is rotatable through a sleeve 4I on the shaft B and actuates by means of a gear-wheel 42, one or more pinions 43 each of which is secured to a shaft 44. On this shaft 44 is mounted a gear-Wheel 45A engaging a pinion 46 secured to the member 35 which is in turn connected to the shaft II driving the rotor I2 of `the compressor.

A relative tightness of the chambers 28 and 29 is ensured by the clearance existing at 41 between the member 3D and the members 3| and 32. Calibrated orifices 48 pierced in the members 33 and 34 provide for the discharge of the oil coming from 41. Other calibrated orifices 49 pierced in the operative parts 3| and 32a of the respective members 3| and 32 provide for their lubrication before the clutching takes place.

The operation is as follows. The pinions or torque limiting members 2, 3, 4 are actuated by the shaft I, and they rotate the pinion or driving member and hence the shaft 6 at one of the 4bers 28 and 29 which are situated between av the reduction of the ineiective time'required for speeds of rotation intended for the compressor.

In order to obtain the first speed, or direct drive, the distributer 25 is so disposed as to circulate the fluid under pressure on the path 24, 22, 20, 21 between the members 30 and 32. The pressure ensures the coupling of the members 32 and 34, and the driving of the rotor I2 of the compressor at the speed of rotation of the shaft 6. As the member 35 is in contact at 50 with the ring I5 it is the member 30 and hence the shaft 6 which is displaced.

I n order to drive the compressor at the second speed, the distributer is rotated so as to cut off the supply of oil through 24, 22, 20, 21 and to establish it through 23, 2|, I9, 26.` The chamber 29 between the members 30 and 32 is emptied of oil by the action of centrifugal force, owing to the imperfect sealing existing at 41, and at the same time, the pressure becomes established in the chamber 28 between themembers 30 and 3|,

chamber 28 is sufcient, the shaft 8 slides and uncouples themembers 32 and 34, While coupling 3| and 33. The member 3| then actuates the compressor by means of the set o gearing 42, s than that of the shaftv B, according to the gearatio in use.

It shouid be noted that it is preferable to give the operative parts of the coupling members the tapered'form as this prevents the facings 33a the passage of one speed to another, and thus diminishes the heat produced.

In some cases, the mechanism can serve to limit the torque.

It should be further noted that the clutch discs rotate at one of the driving speeds oi the compressor, that is at a relatively high speed, and the driving torque is much less than if the clutch were mounted on the shaft I and rotated at a slower rate. For this reason, the mechanism contained in the casing I1 has but a small size.

The aforesaid mechanism has theform of a separate device which can be readily dismounted from the compressor. This latter is arranged so that in this case it may be operated by a direct drive` Figs. 1 and 2 show an example which can be realized without dismounting the compressor. The interior of the tubular shaft II comprises a fiuted portion 5| adapted to engage the iiuted end of an auxiliary shaft 52 thus forming a splined connection (Fig. 2), said shaft having a splined connection at its other end with the bore 1 of the `pinion or driving member 5. A stoppiece 53 (Fig. 2) mounted in the groove 54 (Fig. l) serves to prevent the disengagement of the shaft 52. Acover 55 which is mounted in the place of the casing I1, serves to enclose the whole.

For effecting this mounting it is necessary to remove the ring I5 (Fig. 1), but it is possible to.

use any other connecting means, for example through the member 39'Which would not necessitate the removal of said ring.

Obviously, the invention is not limited to the embodiment herein described and represented, which is given solely by way of example.

Having now described my invention what I claim as new and desire to secure by Letters Patent is: 1. A compression arrangement of the type described comprising a centrifugal compressor including a casing I8 and a rotor I2, a tubular shaft I| rotatably supported in said casing, said rotor I2 being secured to said tubular shaft II, a driving mechanism located on one side of said compressor and including a driving shaft I, a driving member 5 coaxially and rotatably mounted with 'relationto said tubular shaft, a speed increasing gear 2-4 connecting said driving shaft and said driving member 5 and having such a transmission ratio as to rotate said driving member 5 at one speed desired for said rotor, and separate dismountable torque transmitting means located on the opposite free end pf said compressor, including an auxiliary shaft 6 or 52 coaxially 'and rotatably mounted within said tubular shaft, splined'connecting means 1 adapted to connect as to rotation said driving member 5 with the adjacent end of said auxiliary shaft 6 or 52 and detachable coupling means 52 or 30 to 39 between said auxiliaryshaft 6 or 52 and said tubul'anshaft adapted to connect said auxiliary shaft and said tubular shaftas to rotation.

' 2. A compression arrangement of the type described comprising a centrifugal compressor including a casing I8 and a rotor l2, a tubular -shaft II rotatably supported in said casing, said rotor I2 being secured to said tubular .shaft II,

a driving mechanism located on one side of said compressor and including a driving shaft I, a driving .member 5l coaxially and rotatably mounted with relation tosaid tubular shaft, a

speed increasing gear 2-.4 connecting said driving shaft and said driving member 5 and having such a transmission ratioasto'rotate said driv- Y ed with renden to said tubular shaft, a speed said auxiliary shaft and said tubular shaft.

adapted to aiord selectively a direct drive oi said tubular shaft and at least one transmission ratio diierent from I.

3. A compression arrangement of the type described comprising a centrifugal compressor including a. casing I8 and a rotorfl2, a tubular shaft II-rotatably supported in said casing, said rotor I2 being secured to said tubular shaft I I,

a'driving mechanism located on one side of said compressorand including a driving shaft I, a

member 5coaxia1ly and rotatably mountincreasing gear 2'-4 connecting said driving shaft and said driving member 5 and having such a transmission ratio as to rotate said driving member 5 at one speed desiredl for said rotor, and separate dismountable torque transmitting means located on the opposite free end of said compressor, including an auxiliary shaft 5 or 52 coaxially and rotatably mounted within said tubu.

lar shaft, splined connecting means 'I adapted to connect as to rotation said driving member 5 with the adjacent end of said auxiliaryshaft 6 or 52 and a `housing removably secured to said casing on the opposite side of said rotor, including a driven member 35 slidably connected i'or rotation with said tubular shaft II, a change speed mechanism in said-housing between said'auxiliary shaft and said tubular shaft, adapted to aiord selectively between said auxiliary shaft and said driven member a direct drive and at least one positive transmission ratio different from 1, whereby said housing, said change speed mecha.- nism, said driven member and said dismountable torque transmitting means can be withdrawn and simplified connecting means can be adapted to connect said driving member with said tubular shaft as to rotation at one speed only.

HENRY CHARLES ALEXANDRE Po'mz. 

